This invention relates to an apparatus for treating fibre suspensions by screening (centrifugal screening) and fibre-separating mechanical working (refining), for example in water, air or steam, for the manufacture of papermaking pulp. The treatment has the object to clean the suspension by screening of enclosed coarse particles, as for example fibres not sufficiently separated, fibre bundles (shives), and to subject the coarse fraction to a fibre-separating mechanical treatment, by which this fraction is converted to dimensions acceptable in the cleaned fraction.
The present state of art has solved the screening problem by using separate screening devices and connected thereto separate devices for the treatment of the separated coarse reject fraction. This combination, however, involves the problem that available screening devices require for optimum function a very low fibre/water concentration (normally 1-4%), while the beating devices require for optimum development of strength and quality a much higher concentration (normally 10-30%). This necessitates expensive dewatering devices between screening and reject treatment and consequently much space-requiring storage containers and extensive pump work.